The side mirrors were moved from the A-pillar to the door and made smaller and shaped to reduce drag and wind noise.
As seen on the 2013 Mustang GT, the new 2015 also forgoes the fake scoops of yore for functional vented hoods to improve cooling and reduce lift.
With a unique styling design, the front bumper and fender meet on the top of the jointed crease. The hood is quite curvaceous with very sharp angles that are very pronounced at certain angles.
The rear decklid was lowered 2.8” and a slight up-kick is a nice styling cue that should help downforce and drag slightly. There are many manufacturers from Roush to RTR that extend or enhance this angle with a bolt-on spoiler. I feel that it will be a very popular modification to improve the looks and handling of the car.
As you move up from the V6 to EcoBoost to GT, and add the Performance Package on top of that, the aerodynamics improve with each step. The base model cars have a flimsy air dam to prevent air from going under the car and creating turbulent lift and drag, while the performance package cars have large protruding splitters with a smooth underside like the GT PP above.
The GT Performance Package even has front diffusors that direct the air to Porsche-like air deflectors on the front control arms send air to cool the brakes.
The body-colored diffusor is tucked up and out of the airstream below the car to reduce drag by not act like a parachute compared to low hanging rear bumper designs.